Photovoltaic structures found in solar cells are semiconductor structures that convert photons into electricity. In general a photovoltaic cell performs photo-generation of charge carriers (electrons and holes) in a light-absorbing material and separates the charge carriers to a conductive contact that will transmit the electricity. The conversion process of a photovoltaic cell is referred to as photovoltaic effect. The photovoltaic effect allows a solar cell to create solar energy.
One type of photovoltaic cell is a multi-junction cell such as a triple-junction solar cell. Conventional triple-junction solar cells consist of GaInP and GaAs subcells on a p-type Ge substrate. A third subcell is formed by the near-surface doping of the Ge substrate with As to form an n-p junction. The device structure consists of GaInP, GaAs, and Ge subcells separated by heavily-doped tunnel-junctions to enable efficient electrical contact between the cells. Germanium compound semiconductor based triple junction cells currently provide the highest efficiencies for solar cells and are potentially applicable to the optical concentrator market. However, using germanium as a wafer for multi-junction solar cells has drawbacks such as the resulting weight of the final device. Also, germanium is an expensive material and a non-plentiful material.
Therefore a need exists to overcome the problems with the prior art as discussed above.